The so-called waterless cooking method involves the cooking of food, particularly vegetables, using relatively small amounts of water. This method preserves the nutrients of the food by using lower temperatures and also conserves energy. For example, frozen food can be cooked from its frozen state without the addition of water other than the water which is already frozen in. Other types of food will require small amounts of water, for example, as little as one tablespoon. The waterless cooking method requires a covered pan or container in which the cover is equipped with a device that indicates when the water starts to boil. When this occurs, the container outlet should be closed and the heat should be reduced to its lowest value thereby creating a vacuum in the container. The creation of a vacuum permits the food to cook properly at lower temperatures.
One type of waterless cookware presently on the market have pan covers with closable vent systems. The vent system is built in the cover knob and includes a whistle which indicates when the water is boiling. The vent can be closed to create a vacuum in the cooking pan. The cover knob includes a tubular base which is installed in a pan cover opening and has a flange at its lower end which engages the undersurface of the cover. An opening is provided in a wall at the upper end of the tubular base and a thread is formed on the exterior of the tubular base. A tubular upper portion telescopes over the tubular base and it has an internal thread which engages the external thread of the base. A vent passage outlet is formed in a wall at the top of the upper tubular portion. An annular housing fits over the telescoped tubular portions and this housing has a vent opening in the top thereof and a slidable plate to close the vent passage outlet of the upper tubular portion.
The vent knob described above has presented several problems in manufacture and use which the knob of this invention is intended to correct. First, the knob presently on the market is expensive to manufacture. One reason for its high cost of manufacture is that it is held together by metal screws which increase its complexity and thus its cost of manufacture and assembly. Secondly, the slidable plate which shuts off the vent passage requires integral plastic resilient tabs for sealing. This means the slide plate must be manufactured to close and expensive tolerances. Thirdly, the vent opening is located in the top of the knob and presents the danger of scalding to the user since any steam generated by the boiling water is discharged at the top of the knob, where it can contact the hand of the cook.
In contrast, the knob of this invention has none of the foregoing deficiencies. The knob of this invention is less expensive to mold and assemble than the previously discussed knob since no fasteners are required for its assembly. Secondly, since the vent opening of the knob of this invention is closed by gravity movement of a disc, resilient tabs for the closure member are not required. Thirdly, any steam generated during this boiling of the water is discharged near the base of the knob where it is less likely to cause injury to the cook.
Additionally, the knob of this invention will automatically re-open the vent if the heat is not properly reduced after the vent is closed and will indicate the re-opening of the vent by a whistling sound.
These advantages and others will be found in the following specification, claims and drawings.